Patent Literature 1 describes a filter device 2 for preventing an influence of dust, soot, and the like on a projector 3 provided in a poor environment, as shown in FIG. 1 thereof. The filter device 2 includes an external casing that includes an air intake window 10 covered by a filter unit 14, a fan 15 that blows cooling air onto the projector 3, and a discharge window 11 provided in front of a discharge port 6 of the projector 3. The projector 3 is set in the external casing 13, and these are attached to a lid plate portion connected to a ceiling hanger (both of which are not numbered) (paragraphs [0013], [0017], [0023], etc. in specification of Patent Literature 1).
Patent Literature 2 describes a projector case 1A in which, as shown in FIG. 5 thereof, an internal space is divided into a first space H1 including a ventilation port 3 and a ventilation fan 5 and a second space H2 including an exhaust port 4 and an exhaust fan 6. In this projector case 1A, the ventilation fan 5 and the exhaust fan 6 are controlled on the basis of a temperature difference between an external temperature and a temperature of the second space H2. Accordingly, a driving state of a projector can be controlled in accordance with an operation state thereof, and running costs can be suppressed (paragraphs [0018], [0021], etc. in specification of Patent Literature 2).